Reducing unintentional injuries is one of the top ten priorities of the Healthy People 2010 initiative. Injury prevention clearly plays an integral role in children's health, as unintentional injuries are the leading cause of death in children and young adults. Bicycle crashes are among the most common causes of severe injuries in late childhood and early adolescence. Motor vehicles are involved in approximately one-third of all bicycle- related brain injuries and in 90% of all fatalities resulting from bicycle crashes. A critical first step in developing programs to prevent collisions between child cyclists and motor vehicles is understanding why such collisions occur. The goal of this multi-disciplinary research proposal is to examine how immature perceptual-motor functioning puts children at risk for car-bicycle collisions when crossing roads. Using an immersive, interactive bicycling simulator, we will examine how two important aspects of perceptual-motor development influence road-crossing behavior. The first is coordinating motor movement with visual information. A robust finding from our research on children's road-crossing behavior is that children choose the same size gaps as adults, but leave less headway when they start to cross. Consequently, child cyclists end up with far less time to spare when they clear the path of the oncoming car. This puts child cyclists at greater risk for a collision because they have less time available to recover from an error such as a foot slipping off the pedal. The second aspect of perceptual-motor development we will address is flexibly adapting movement to changing circumstances. Skilled road crossing requires that cyclists adjust quickly to changes such as the distribution of gap sizes. The first set of proposed experiments will test hypotheses about why children leave less headway when starting off than do adults. These include 1) immature movement preparation strategies, 2) problems with making "go-no go" decisions, and 3) difficulty with synchronizing self and object movement. The second set of experiments will examine how children adjust their road-crossing behavior in response to changing circumstances and how these experiences influence later road-crossing behavior. By bringing together the study of basic and applied issues into a single program of research, this work will contribute both to our understanding of the development of perceptual-motor functioning and to our understanding of the underlying causes of child bicycling injuries. '